Abstract:Based on some theoretical analyses and available experiment achievements,the author expouns that the slope thresholds are not constant,and are functional relationship with the runoff depth,sediment particle and vegetation cover.The siope thresholds are all greater than 40 degree.

Abstract:The features of sediment-producing by erosion of steep slope land in loess hilly regions were analised ,The course of sediment-producing by erosion and sediment-producing amount by rainly erosion have been studied by using the simulated experiments of artificial rainfall and the data of natural runoff plots.At the same time,the regressional analysis have been carried out between sediment-producing amount by splash erosion and its influencing factors.The results show that the sediment-producing amount by splash erosion accounts for from 22 per cent to 54 per cent of the toral sediment-producing amount in the simulated experiments.The calculation model for the sediment content course of sediment-producing by rainfall erosion were developed based on the experimental researches and developing model.The test on this model shows that the model has a composition and a better applicative.

Abstract:The optimization pattern of afforesative techniques with collecting runoff with collecting runoff to drough-resistance was presented by using L₉（3⁴）plan in the orthogonal experiments.It has shown that the order of four factors contributed to afforestative species(A)>cover material in the planted pits (D)>collection area of runoff for each tree(B)land preparation for afforestation(C).Of all factor,the order of the same kind is as follow;for A,Robinia pseudoacaia L.>Ulmus Pumila>Plalycladus arientalis Franco;For D,film>foam matcial>straw;for B,2.5m²>2.0m²>1.5m²;and for C,reverse slope terrace>level furrom>fish-scale pits.In semiarid loess hilly areas,the optimization pattern of afforestative techniques with collecting runoff to drough-resistance is A,D,B,C,Namely,afforeatative species is Rohinia Pseudoacacia L;the cover material of planted pits is film,the collectiom area of runoff for each tree is 2.5m²,and the land preparation pattern for afforestation is reverse slope terrace.

Abstract:The soil particle composition of grassland is affected slightly by the cover-degree and yield of grass in the loess Plateau.It is mainly affected by the distribution of soil zonality of soil zonality.The volume weighet and total porosity of grassland are affected by the cover-degree and yield of grass.When the cover-degree and yield are low,the soil volume weight is greater than or equal to 1.20g/cm²and the soil tatal porosity is around 55%;with the increase in them,the soil volume weight will become less than or equal to 1.20g/cm² and soil total porosity become greater than or equal to 50%.When the cover-degree and yield are low,there phase ratio of solid,liquid and gas for grassland is 1∶0.10～0.19∶0.60～0.90;conversely,that raito become 1∶0.33～0.75∶1.15～1.76.The soil physical properties of grassland are correlated with litter layer and content of soil organic matter.The soil physical properties and the density of root system are keys to improve characteristics of soil hydraulics,to strength soil anti-scaurability and infiltraion,and to increase slope stability.

Abstract:A regressional equation of soil loss amount on slope land,which suits for Dabieshan area of Anhui province,has been developed using the investigative data in this area and the multiple regressional algorithm.It will provide a quantitative tool for the monitor and forecast of soil and water loss and the control work in small watershed.

Abstract:The serious effects of sand gold mining on soil fertility were reported in this paper.These effects include,the structure of soil section was broken,gravel and bottom soil were reversed to surface soil,the nutrients of top tilling soil lost serious,the soil fertility and crop fertility and crop yield decreased.With the above results,the authors suggested that the keys of soil fertility conservation in soil reclamation should be to come off soil layer by layer and to place the topsoil alonely in sand gold mining.The heart of the matter is to carry on artificial plough in place the topsoil alonely in sand gold mining.The heart of the matter is to carry is to carry on artificial plough in paddy soil reclamation in the sand gold mine region of south China.

Abstract:On the Basis of summarizing practical experience,and of combining theory with practice,the theoretical calculation formula to design level through was derived was derived.The algorithms to calculate economic section and double pitch function were presented.The construction pattern that combines economic benefit with hillside development and takes level through as a centre was approached.At the same time,the main points designing,arrangement and construction features,functional superiorities and suitable range of level through have been dealt with.

Abstract:Having bilt forest of Hippophae rhamnaides Linn.in the slope of Debrits Flow Red Earth(DFRE),the changes of soil moisture and temperature in the surface soil become more evenly.The ten-years forest has shown its improving effects on the soil.The physical and chemical properties of the soil have been improved at the different degrees.The biomass of Hippophae rhamnaides Linn.in DFRE is second only to that in the shaddy ditch slope,and is more than that in the other conditions

Abstract:Based on fundamental principle of planting grass seed with waterpower,the technique was applied to control soil and water loss in the projects of water conservancy in Guangdong province.By using this technique,the objectives to protect slope,to control soil and water loss and to afforest environment have been achieved.Meanwhile,the prospects of this technique for application and popularization in the control on soil and water loss were analysed.

Abstract:In this paper,a method drawing contour map by microcomputer is introduced into soil erosion field.The method is very easy to learn and to operate without special traning,and the software required are common.It overcomes many defects caused by hand-drawing.A simple and practical technique for drawing contour map is provided for the soil erosion researchers.

Abstract:The soil and water loss in the uncultivated slope land of fragmental soil,the cultivated slope land of fragmental soil and loess were observed and studied in Luanping central experiment area.The results shown that the amount of runoff and erosion each year in cultivated slope land of fragmental soil accounts for only 8 per cent and 1 per cent of that in loess respectively.It was poilted out that the main contoroled land for soil and water loss is the cultivated slope of loess in this area.